CO Anatomy, Biomechanics & Pathophysiology of the Musculoskeletal System 2 — Questions and Answers
Question 1: Which ligament is the primary restraint to anterior translation of the tibia on the femur?
- Posterior cruciate ligament
- Anterior cruciate ligament (Correct answer)
- Medial collateral ligament
- Lateral collateral ligament
Correct answer: Anterior cruciate ligament
The anterior cruciate ligament (ACL) is the primary restraint preventing anterior tibial translation relative to the femur.
Question 2: The subtalar joint axis orientation primarily governs coupling between which two motions?
- Plantar flexion and dorsiflexion
- Inversion and eversion coupled with tibial rotation (Correct answer)
- Abduction and adduction only
- Metatarsophalangeal flexion and extension
Correct answer: Inversion and eversion coupled with tibial rotation
The oblique subtalar joint axis couples subtalar inversion/eversion with internal/external tibial rotation during gait.
Question 3: In spastic cerebral palsy, the pathophysiologic basis for increased muscle tone is best described as:
- Peripheral nerve demyelination reducing motor conduction velocity
- Upper motor neuron lesion causing loss of inhibitory control over the stretch reflex (Correct answer)
- Lower motor neuron destruction reducing alpha motor neuron firing
- Damaged Golgi tendon organs losing inhibitory feedback
Correct answer: Upper motor neuron lesion causing loss of inhibitory control over the stretch reflex
Spasticity results from an upper motor neuron lesion that releases the stretch reflex from descending inhibitory control, causing velocity-dependent tone increase.
Question 4: Which bone of the foot serves as the keystone of the medial longitudinal arch?
- Navicular (Correct answer)
- Talus
- First cuneiform
- Cuboid
Correct answer: Navicular
The navicular bone acts as the keystone of the medial longitudinal arch and is the primary site of arch collapse in adult flatfoot.
Question 5: During normal gait, ground reaction force (GRF) passes anterior to the knee joint at approximately which phase?
- Loading response
- Initial contact
- Mid-stance (Correct answer)
- Terminal stance
Correct answer: Mid-stance
During mid-stance, the GRF vector typically passes anterior to the knee axis, creating an extension moment that reduces quadriceps demand.
Question 6: The condition known as 'windlass mechanism' in foot biomechanics involves passive tension in which structure?
- Achilles tendon
- Plantar fascia (Correct answer)
- Spring ligament
- Tibialis posterior tendon
Correct answer: Plantar fascia
The windlass mechanism describes plantar fascia tension created by toe dorsiflexion, which raises the medial arch and supinates the foot during push-off.
Question 7: Charcot-Marie-Tooth disease most commonly causes orthotic need due to weakness of which muscle group?
- Hip abductors and knee extensors
- Ankle dorsiflexors and evertors with high-arched foot (Correct answer)
- Wrist extensors and intrinsic hand muscles only
- Proximal lower extremity muscles with preserved distal function
Correct answer: Ankle dorsiflexors and evertors with high-arched foot
CMT typically causes a length-dependent peripheral neuropathy leading to ankle dorsiflexor and evertor weakness, producing foot drop and a cavovarus deformity.
CO Anatomy, Biomechanics & Pathophysiology of the Musculoskeletal System 2
Which ligament is the primary restraint to anterior translation of the tibia on the femur?